<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>标准盒与怪异盒</title>
  <link rel="stylesheet" href="./css//3_case.css">
</head>
<body>
  <div class="case1"></div>
  <div class="case2"></div>

  <div class="case3">
    <div class="mtd1">div1</div>
    <div class="mtd2">div2</div>
    <div class="mtd3">div3</div>
  </div>
  <div class="case4">
    <h1>粘性定位</h1>
  </div>
</body>
</html>